1. Field of the Invention
The present invention relates to heat recovery systems, and in particular relates to such systems which recover the waste heat of air conditioning and refrigeration systems for purposes of heating water.
2. Description of the Prior Art
Because of the rapidly rising costs of energy, the incentives to conserve energy are increasing, both for industrial users and domestic users. Consequently there is currently considerable interest in not only eliminating energy waste by making equipment more efficient, but also by recovering energy such as waste heat which, according to conventional practice, is usually injected into the atmosphere without recovery.
It is well known in the art to use some of the heat from the condensing process of a refrigeration system to produce hot water in a storage tank. Heat is reclaimed by installing a heat exchanger in the hot gas line between the compressor and the condenser of the air conditioning system. Water from the bottom of the hot water heater tank is circulated through the heat exchanger by means of a small circulating pump. This basic arrangement has been used with success and is gaining widespread acceptance; but there is continuing interest in improving this basic system to make it more efficient and responsive.
The potential for energy conservation by the recovery of waste heat in the home and in industrial applications is substantial because of the amount of energy required to operate air conditioning equipment and hot water heating equipment, both of which are significant users of energy. For example, an air conditioning system with a water cooled condenser, while producing a ton of refrigeration or 12,000 BTUH of cooling capacity, also produces approximately 15,000 BTUH of heat which is rejected to the atmosphere. An air conditioning system with an air cooling condenser rejects about 16,000 to 17,000 BTUH for each ton or 12,000 BTUH of cooling capacity. Of this 15,000 to 17,000 BTUH of heat for each ton of capacity, 3,000 to 5,000 BTUH is relatively easy to recover at a very nominal expense. Generally, the refrigeration system is operated totally separate from the hot water system with the result that the heat removed from the condensing process is wasted, while the water in the hot water system is heated by means of an auxiliary energy source such as gas, electricity, or oil. The cost of such fuel or energy can be great particularly in situations where large amounts of hot water are required.
In industrial applications, many large refrigeration compressors are used in freezing, refrigerating or air conditioning. The recoverable heat associated with the hot refrigerant gases produced by the refrigeration compressors may be utilized in connection with an ongoing industrial process. However, most industrial installations can use some of the heat in the form of hot water. Because of the large volume of refrigerant flowing in industrial refrigeration compressor systems, and the necessarily large size refrigerant lines required, the conventional in-the-line (series) heat exchanger cannot be used for heat exchange purposes because of the detrimental effect of its large fluid flow resistance which causes an unacceptable pressure drop in the system. On the other hand, a heat exchanger connected in parallel with the refrigerant line would have a higher resistance to flow than the refrigerant line and therefore an insufficient volume of refrigerant gas would pass through the heat exchanger for heat exchange purposes. Accordingly, it is desirable to provide a waste heat recovery system in which a predetermined fraction of the high pressure heated refrigerant vapor flow can be diverted through the refrigerant passage of a heat exchanger for heat exchange purposes without interfering with operation of the compressor system.